Cryogenic phase separator



Jan. 2, 1968 J. H. FRETWELL. ET AL 3,360,947

CRYOGENIC PHASE SEPARATOR Filed April 27, 1966 INVENTORS James H. F re/we/l,

Hugh K. Jennings United States Patent Ofiice 3,360,947 Patented Jan. 2, 1968 3,360,947 CRYOGENIC PHASE SEPARATOR James H. Fretwell and Hugh K. Jennings, Los Alamos, N. Mex., assignors to the United States of America as represented by the United States Atomic Energy Commission Filed Apr. 27, 1966, Ser. No. 546,478 2 Claims. (CI. 62-45) ABSTRACT OF THE DISCLOSURE A liquid cryogen transfer device consisting of a thin stainless steel cylinder that is perforated at its inlet end, loosely filled with stainless steel wool, and is thermally insulated.

The invention described herein was made in the course of, or under, Contract W-7405-Eng-36 with the US. Atomic Energy Commission.

This invention is concerned with a device which separates a liquid cryogen from its gaseous phase and thus permits the liquid cryogen to drain by gravity in a quiescent manner into a suitable container or Dewar.

The methods of obtaining quiescent cryogenic fluid transfer as contained in the prior art were restricted in their application to devices that were placed Within the Dewar being filled while the device of this invention can be used outside the Dewar vessel proper and therefore has utility in filling a narrow mouth Dewar. The filling of individual liquid cryogen cold traps (which are employed in the high vacuum systems of most accelerator beam tubes, for example) by manual means from small Dewars has been a standard practice at most laboratories. Most of these traps required filling twice a day, seven days a week, and resulted in considerable amount of labor and v was quite ineflicient in the transfer of the liquid cryogen from its storage vessel to the Dewar within the cold trap system. The cryogen is transferred from a storage vessel through a /2-inch foam insulated transfer line and it is during the cooldown of this transfer line that large quantities of gas are evolved from the liquid cryogen. In any cryogen transfer system of saturated liquid it is clearly evident that a large quantity of gas will be evolved from the heat leak of ambient temperature into the transfer line. This forms quantities of bubbles constituting the gas phase of this cryogen. In addition, the release of pressure of the cryogen stored at a saturated temperature within the supply Dewar to that reduced pressure of the atmosphere within the trap Dewar always generates the gaseous phase of the cryogen.

It is therefore not desirable to allow this warm gas to flow directly into the cold trap since this would tend to evaporate the cryogen already there. To separate the useful fraction of liquid cryogen out of the high velocity gas stream a phase separator external to the trap was necessary and is the subject of this invention. This phase separator, as designed by the inventors, consists essentially of a thin, stainless steel cylinder which is insulated and loosely filled with stainless steel wool. During operation the gas escapes through large holes in the top of the said cylinder while the liquid cryogen which is influenced by gravity flow downward to the trap. In order to reduce cooldown losses, it is essential that the mass of the phase separator be kept to a minimum and the inventors have found through experiment that the weight of each phase separator must be limited to approximately 500 grams or less.

It is therefore an object of this invention to provide a device for the efficient transfer of liquid cryogens from a pressurized storage vessel to a Dewar.

Other objects of this invention will be apparent from the following description when read in connection with the accompanying drawing in which the figure is a three quarter sectional view of the phase separator constructed in accordance with the invention.

The preferred embodiment of the present invention shown in the figure comprises a stainless steel tube 1 through which the liquid and gaseous phases cryogen enter into a lightweight cylinder 4 filled with a loosely packed coarse steel wool 2, and said cylinder being surrounded by any suitable cryogenic insulation 3, usually foam, and said cylinder 4 being perforated at the inlet end with a multiplicity of holes 5 through which the gaseous phase of the cryogen escapes upward while the liquid phase by gravity flows downward through the steel wool 2 and exists the cylinder through the small outlet stainless steel tube 6.

The essence of this invention is a device to separate a liquid cryogen from its gaseous phase and which was previously contained at higher pressures in a storage system, thus permitting the cryogen to drain by gravity in a quiet manner to a separate Dewar or container. This device consists of a vertical cylinder loosely filled with stainless steel wool into which a two-phase mixture is presented at the center of the upper end; the gas phase escapes through large holes at the upper end while the liquid phase boils to a lower pressure and drains from a smaller tube at the lower end.

Thus it is apparent that the present invention provides a simple, compact cryogenic transfer device which may or may not be placed within the transfer Dewar. While the presently preferred embodiment of the present invention has been described, it is clear that modifications may be made without departing from the scope of the invention. Therefore, the present invention is not limited by the foregoing description but solely by the appended claims.

What is claimed is:

1. A liquid cryogen transfer device for separating the liquid phase from combined cryogenic liquid and gaseous phases comprising an enclosed thin metal cylinder, said cylinder having a liquid cryogen entry inlet tube at one end and a liquid cryogen outlet tube at the other end, thermal insulation means surrounding the cylinder, coarse steel wool loosely filling the inside of the cylinder, means allowing the gaseous phase to escape, said means constituting multiple perforations in the cylinder end supporting the inlet tube.

2. The device of claim 1 in which the cylinder and the inlet and outlet tubes are constructed of stainless steel and are of approximately the same diameter.

References Cited UNITED STATES PATENTS 3,126,711 3/1964 Miller 62-55 3,201,947 8/1965 Post et a1. 62-55 3,206,939 9/1965 Wilson 62-65 3,296,809 1/1967 Feuerstein 6245 LLOYD L. KING, Primary Examiner. 

